Petroleum drilling industry.

Oil and natural gas drilling rigs are used not only to identify geologic reservoirs but also to create holes that allow the extraction of oil or natural gas from those reservoirs. Primarily in onshore oil and gas fields once a well has been drilled, the drilling rig will be moved off of the well and a service rig (a smaller rig) that is purpose-built for completions will be moved on to the well to get the well on line. This frees up the drilling rig to drill another hole and streamlines the operation as well as allowing for specialization of certain services, i.e., completions vs. drilling.

Water well drilling.

New portable drillcat technology uses smaller portable trailer mounted rigs with shorter 3-metre (10 ft) drill pipe. The shorter drill pipe also allows a much smaller mast. Portable trailer mounted drilling rigs have drill ratings from 90 to 200 metres (300 to 800 ft) depending on mud pump flow and pressure ratings and drill pipe sizes.

Other, heavier, truck rigs are more complicated, thus requiring more skill to run. They're also more difficult to handle safely due to the longer 6-to-9-metre (20 to 30 ft) drill pipe. Large truck rigs also require a much higher overhead clearance to operate. Large truck drills can use over 570 litres (150 US gal) of fuel per day, while the smaller Deeprock Style portable drills use a mere 20 to 75 litres (5 to 20 US gal) of fuel per day. This makes smaller, more portable rigs preferable in remote or hard-to-reach places, and they are more cost effective when fuel prices are high.

Mobile drilling rigs.

In early oil exploration, drilling rigs were semi-permanent in nature and the derricks were often built on site and left in place after the completion of the well. In more recent times drilling rigs are expensive custom-built machines that can be moved from well to well. Some light duty drilling rigs are like a mobile crane and are more usually used to drill water wells. Larger land rigs must be broken apart into sections and loads to move to a new place, a process which can often take weeks.

Small mobile drilling rigs are also used to drill or bore piles. Rigs can range from 100 ton continuous flight auger (CFA) rigs to small air powered rigs used to drill holes in quarries, etc. These rigs use the same technology and equipment as the oil drilling rigs, just on a smaller scale.

The drilling mechanisms outlined below differ mechanically in terms of the machinery used, but also in terms of the method by which drill cuttings are removed from the cutting face of the drill and returned to surface.